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#ifndef UNITY_ATMOSPHERIC_SCATTERING_INCLUDED
#define UNITY_ATMOSPHERIC_SCATTERING_INCLUDED
#include "CoreRP/ShaderLibrary/VolumeRendering.hlsl"
#include "CoreRP/ShaderLibrary/Filtering.hlsl"
#include "AtmosphericScattering.cs.hlsl"
#include "../SkyVariables.hlsl"
#include "../../ShaderVariables.hlsl"
#include "../../Lighting/Volumetrics/VBuffer.hlsl"
#if (SHADEROPTIONS_VOLUMETRIC_LIGHTING_PRESET != 0)
TEXTURE3D(_VBufferLighting);
#endif
CBUFFER_START(AtmosphericScattering)
int _AtmosphericScatteringType;
// Common
float _FogColorMode;
float4 _FogColorDensity; // color in rgb, density in alpha
float4 _MipFogParameters;
// Linear fog
float4 _LinearFogParameters;
// Exp fog
float4 _ExpFogParameters;
CBUFFER_END
#define _MipFogNear _MipFogParameters.x
#define _MipFogFar _MipFogParameters.y
#define _MipFogMaxMip _MipFogParameters.z
#define _FogDensity _FogColorDensity.w
#define _FogColor _FogColorDensity
#define _LinearFogStart _LinearFogParameters.x
#define _LinearFogOneOverRange _LinearFogParameters.y
#define _LinearFogHeightEnd _LinearFogParameters.z
#define _LinearFogHeightOneOverRange _LinearFogParameters.w
#define _ExpFogDistance _ExpFogParameters.x
#define _ExpFogBaseHeight _ExpFogParameters.y
#define _ExpFogHeightAttenuation _ExpFogParameters.z
float3 GetFogColor(PositionInputs posInput)
{
if (_FogColorMode == FOGCOLORMODE_CONSTANT_COLOR)
{
return _FogColor.rgb;
}
else if (_FogColorMode == FOGCOLORMODE_SKY_COLOR)
{
// Based on Uncharted 4 "Mip Sky Fog" trick: http://advances.realtimerendering.com/other/2016/naughty_dog/NaughtyDog_TechArt_Final.pdf
float mipLevel = (1.0 - _MipFogMaxMip * saturate((posInput.linearDepth - _MipFogNear) / (_MipFogFar - _MipFogNear))) * _SkyTextureMipCount;
float3 dir = -GetWorldSpaceNormalizeViewDir(posInput.positionWS);
return SampleSkyTexture(dir, mipLevel).rgb;
}
else // Should not be possible.
return float3(0.0, 0.0, 0.0);
}
// Returns fog color in rgb and fog factor in alpha.
float4 EvaluateAtmosphericScattering(PositionInputs posInput)
{
float3 fogColor = 0;
float fogFactor = 0;
switch (_AtmosphericScatteringType)
{
case FOGTYPE_LINEAR:
{
fogColor = GetFogColor(posInput);
fogFactor = _FogDensity * saturate((posInput.linearDepth - _LinearFogStart) * _LinearFogOneOverRange) * saturate((_LinearFogHeightEnd - GetAbsolutePositionWS(posInput.positionWS).y) * _LinearFogHeightOneOverRange);
break;
}
case FOGTYPE_EXPONENTIAL:
{
fogColor = GetFogColor(posInput);
float distance = length(GetWorldSpaceViewDir(posInput.positionWS));
float fogHeight = max(0.0, GetAbsolutePositionWS(posInput.positionWS).y - _ExpFogBaseHeight);
fogFactor = _FogDensity * TransmittanceHomogeneousMedium(_ExpFogHeightAttenuation, fogHeight) * (1.0f - TransmittanceHomogeneousMedium(1.0f / _ExpFogDistance, distance));
break;
}
case FOGTYPE_VOLUMETRIC:
{
#if (SHADEROPTIONS_VOLUMETRIC_LIGHTING_PRESET != 0)
float4 volFog = SampleVolumetricLighting(TEXTURE3D_PARAM(_VBufferLighting, s_linear_clamp_sampler),
posInput.positionNDC,
posInput.linearDepth,
_VBufferResolution,
_VBufferSliceCount.xy,
_VBufferDepthEncodingParams,
_VBufferDepthDecodingParams,
true, true);
fogFactor = 1 - volFog.a; // Opacity from transmittance
fogColor = volFog.rgb * min(rcp(fogFactor), FLT_MAX); // Un-premultiply, clamp to avoid (0 * INF = NaN)
#endif
break;
}
}
return float4(fogColor, fogFactor);
}
#endif